This invention relates to a method and apparatus for cutting valves within veins, specifically, for cutting out vein valves during vascular reconstructive surgery. In particular, it constitutes an apparatus for cutting the valves in a vein in a procedure known as in-situ saphenous vein bypass.
In-situ saphenous vein bypass is a procedure which utilizes the saphenous vein in the human leg, which normally returns blood from the ankle upwardly through the leg, to take over the function of the main artery in the leg after it has become too occluded or otherwise impaired to transport the flow of blood required of it. When the saphenous vein is to be used to take over the function of the artery, it becomes necessary to cut open a series of one-way valves in the vein which, in normal functioning, prevent reverse flow of the blood.
Various valve strippers have been developed over the years for performing this function. Some of these valve strippers have used a valve cutter which is passed through the vein in a direction reverse to the normal direction of blood flow to sever the valves. Examples of such valve cutters include the LaMaitre valvulotome made by Vascutech, Inc. of Massachusetts; the Hall vein stripper made by Cabot Ltd. of High Wycombe, England and the Leather valve cutter made by American V. Mueller of Chicago, Ill. These valve strippers operate blind, that is to say they are passed through the vein without direct observation inside the vein of the positioning of the cutters as they operate. While these devices can perform quite satisfactorily in the hands of an experienced cardiovascular surgeon operating on a vein which does not have complications, blind incision of the valves has serious risks. If the cutter's path veers off course into the side wall, as can happen without the ability to observe it directly, the blades can cut the delicate endothelial lining of the vein with serious adverse consequences. Side branches, i.e., veins entering the main vein from the side, may be caught by the valve cutter and torn open also causing serious injury.
To overcome the disadvantages of blind procedures for cutting the vein valves, an apparatus and method have been devised to view the cutter internally of the vein as it travels by using a fiber optic scope. Such an arrangement is disclosed in Chin et al. U.S. Pat. No. 4,768,508. The Chin patent, in one of its embodiments, discloses a pulling catheter which is inserted into the vein near the ankle, and is passed in the normal direction of blood flow through the saphenous vein and the vein valves until its tip emerges through an exit opening created in the vein. A cutting catheter, which carries a group of four cutting fingers at its end, is attached to the pulling catheter which is then pulled reversely through the vein to cause the cutting fingers to cut through the valves. Each cutting finger is V-shaped with its apex facing the vein sidewall. To enable the surgeon to make observations of the vein during the passage of the cutting catheter along it and to visualize the cutting of each valve, a fiber optic scope is mounted in the cutting catheter for viewing through its advanced, open end.
The apparatus disclosed in the Chin patent has special features. To connect the two catheters together, a wire passes through the length of the pulling catheter and has a V-folded hook at leading end. A button at the opposite end of the wire can be pushed inwardly of the pulling catheter to project the hook to grip a flexible loop attached to the adjacent end of the cutting catheter and then retracted to secure the loop against release. To protect the wall of the vein against gouging by the prong-like cutting fingers during passage through it, a retractably mounted sheath surrounds the cutting catheter. The sheath is advanced along the cutting catheter to enclose the cutting fingers during passage through the vein and is withdrawn from the fingers to expose them only during the cutting of a valve.
While the Chin device is generally satisfactory for the purposes for which it is intended, there are respects in which need exists for improvement. With the arrangement of a retractable hook and loop used in the Chin apparatus for linking the two catheters together, the button for moving the wire hook and the loop on the second catheter are separated by the length of the patient's leg during the performance of the operation. This separation complicates the manipulation of the parts necessary to achieve connection of the catheters. The manipulation back and forth of the slidable sheath also adds a level of complication in operating the apparatus that it would be desirable to eliminate. Also, as the device is advanced between valves with the sheath in the shielding position, the sheath can impair the field of view of the optic scope making it more difficult to observe and avoid side branches.